Ethylene oxide is a gas used to clean roughly half of all sterile medical products involved in patient treatment in the United States, about 20 billion products a year, as reported by Politico.

Ethylene oxide, however, also causes cancer — a fact that the Environmental Protection Agency first acknowledged five years ago, according to Politico. But the EPA and the Food and Drug Administration, the nation’s foremost medical-device safety watchdog, failed to work together until now to avert a massive medical crisis with the potential to affect millions of patients.

Ethylene oxide is a highly flammable, colorless gas that enters the body when inhaled or ingested and causes cancer by damaging DNA, according to the National Cancer Institute. Ethylene oxide is most commonly linked to leukemia and lymphoma, but may also be associated with breast and stomach cancers. 

Earlier this year the Illinois Environmental Protection Agency shut down a factory that used ethylene oxide to sterilize medical devices after discovering unsafe levels of the cancer-causing gas in the surrounding air. According to a statement from the agency, the presence of ethylene oxide exposed workers and the nearby community to “an elevated cancer risk” and represented “a public health hazard to these populations.”

Ethylene oxide factories are shutting down in other states, leaving an untold number of patients in limbo amid possible shortages of lifesaving medical devices like pacemakers, as Politico reported. Meanwhile, residents in the communities surrounding these factories fear they may develop cancer down the line due to exposure to ethylene oxide.

In response, the FDA told Politico it is now working with the EPA and proactively addressing both the health issue of ethylene oxide and potential medical device shortages due to the lack of an acceptable sterilization alternative. The FDA has launched two contests to develop new sterilization techniques and minimize resulting air pollution. It also helped a manufacturer of critical breathing equipment quickly relocate to prevent device shortages.